Bi-invariant metrics and quasi-morphisms on groups of Hamiltonian diffeomorphisms of surfaces

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12 Scopus citations


Let σg be a closed orientable surface of genus g and let Diff0g, area) be the identity component of the group of area-preserving diffeomorphisms of σg. In this paper, we present the extension of Gambaudo-Ghys construction to the case of a closed hyperbolic surface σg, i.e. we show that every nontrivial homogeneous quasi-morphism on the braid group on n strings of σg defines a nontrivial homogeneous quasi-morphism on the group Diff0g, area). As a consequence we give another proof of the fact that the space of homogeneous quasi-morphisms on Diff0(σg, area) is infinite-dimensional. Let Ham(σg) be the group of Hamiltonian diffeomorphisms of σg. As an application of the above construction we construct two injective homomorphisms Zm → Ham(σg), which are bi-Lipschitz with respect to the word metric on Zm and the autonomous and fragmentation metrics on Ham(σg). In addition, we construct a new infinite family of Calabi quasi-morphisms on Ham(σg).

Original languageEnglish
Article number1550066
JournalInternational Journal of Mathematics
Issue number9
StatePublished - 29 Aug 2015
Externally publishedYes


  • Groups of Hamiltonian diffeomorphisms
  • bi-invariant metrics
  • braid groups
  • mapping class groups
  • quasi-morphisms

ASJC Scopus subject areas

  • Mathematics (all)


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